Juniper® JNCIA Exam Cram Notes : Optical Network Fundamentals - Sonet/sdh, Otn

1. Networking Fundamentals

1.3 Optical network fundamentals - SONET/SDH, OTN

Synchronous Digital Hierarchy (SDH) is a CCITT standard for a hierarchy of optical transmission rates. Synchronous Optical Network (SONET) is a USA standard that is largely equivalent to SDH. Both are widely used methods for very high speed transmission of voice and data signals across the numerous world-wide fiber-optic networks.

SDH and SONET use light-emitting diodes or lasers to transmit a binary stream of light-on and light-off sequences at a constant rate. At the far end optical sensors convert the pulses of light back to electrical representations of the binary information.

The basic building block of the SONET/SDH hierarchy in the optical domain is an OC1; in the electrical domain, it is an STS-1. An OC1 operates at 51.840 Mbps. OC3 operates at 155.520 Mbps.

Optical Transport Network (OTN) technology represents both a technical leap forward in optical networking over SONET/SDH and a business opportunity for carriers and service providers alike.

OTN SONET/SDH
Asynchronous mapping of payloads Synchronous mapping of payloads
Timing distribution not required Requires right timing distribution across networks
Designed to operate on multiple wavelengths Designed to operate on multiple wavelengths
Scales to 100Gb/s (and beyond) Scales to a maximum of 40 Gb/s
Performs single-stage multiplexing Performs multi-stage multiplexing
Uses a fixed frame size and increases frame rate to match client rates Uses a fixed frame rate for a given line rate and increases frame size as client size increases
FEC sized for error correction to correct 16 blocks per frame Not applicable (no standardized FEC)





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